Preliminary report of a concurrent validation of a 3 ...

Preliminary report of a concurrent validation of a 3-day diary with accelerometry in a Portuguese sample of adolescents 1

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Aristides Machado Rodrigues , António J Figueiredo , Manuel J Coelho e Silva , Jorge Mota , 3 Robert M Malina 1

Faculty of Sports Science and Physical Education, University of Coimbra, Portugal Research Center in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto 3 Tarleton State University, Stephenville, Texas 2

The purpose of this study was to cross-validate the 3-day physical activity diary proposed by Bouchard et al. (1983) in a Portuguese population. Criterion measures of physical activity were derived using the Computer Science and Application, Inc (CSA) 7164 accelerometer. The sample comprised 98 subjects (boys, n=44; girls, n=54), aged 13 to 16 years old. All participants were volunteers and they wore a CSA monitor for five consecutive days and completed the physical activity diary for the first 3 of those days. The physical activity diary was weakly (ranging between r=+0.28 and r=+0.38) but significantly (p≤.01) correlated with the CSA motion sensor. The results produced coefficients of correlation similar to those obtained in previous studies. These evidences claim for the need to consider physical activity and physical inactivity as independent and complexes variables.

INTRODUCTION Descriptive epidemiological studies of youth physical activity have consistently reported that male subjects are more active than females. Another consensus relates to the physical activity decline during adolescent years (9, 11, 18). As also noted, there is considerable discrepancy on timing and magnitude of these trends (11). This may be, in part, attributable to the complexity of physical activity as an unstable behaviour. It changes over the day, the week, the season, and also over the year. In addition, it should be mentioned the difficulty associated with measuring physical activity, especially among children and adolescents when based in subjective methods such as diaries and questionnaires. The development of accurate methods for monitoring physical activity in children and adolescents continues to be a relevant research issue (14, 17, 20). The easiest, cheapest and most practical method, the questionnaire, is often criticized by its lack of precision, reliability and for some authors validity. The most recommended methods require special equipment and are normally expensive, therefore limited to surveys based on small samples. Children´s patterns of physical activity have been historically assessed by direct observation, selfreport measures, and heart-rate monitoring (12). Activity monitors were developed in response to lack of reliability of questionnaires, the intrusiveness of direct observation, and the complexity and lability of heart-rate monitoring. The accelerometers are an objective measure that is able to provide reliable and valid measures of energy expenditure (1). Unlike questionnaires, 3-day diary involves self-report of physical activity intensity and provides information on frequency as well as the context of energy expenditure. It is not dependent from memory and interpretation. However, the 3-day diary likely might be affected by socially desirable responses, and if not filled out properly, may lead to decreased precision (19). The aim of this study was to validate an adapted version of “physical activity diary” (2) in a Portuguese sample of school adolescents. The validity of diary-derived estimates of total and moderate-tovigorous portions of physical activity is tested by adding CSA 7164 accelerometer a (Computer Science and Application, Inc).

METHODS th

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A sample of 98 Portuguese adolescents was selected from the 7 through 9 grades in a public school located in the Portuguese Midlands - Avelar. The subjects aged between 12 and 16 years, none had physical abnormalities or other diseases. Prior to participation in the study, all subjects provided written assent to participate and their parents provide written informed consent. The Portuguese Commission of Data Protection provided permission to conduct the survey that was also accepted by the scientific committee of the University of Coimbra. Heights and weights were measured following Ross & Marfell-Jones procedures (16). Weight was measured to the nearest 100 grams with the subject wearing light shorts. Heigth was measured to the nearest millimetre with the subject standing with heels together and gently stretched upward (the chin was not lifted). Body Mass Index was calculated. Physical activity was estimated using the activity record developed by Bouchard et al. (1983). A threeday physical activity diary (two week-days and one weekend day) was completed. The activity record divides the day into 96 periods of 15 minutes each. Each period requires the subject to enter a categorical value ranging from 1 to 9 in order to represent the dominant activity. Each categorical value corresponds to an energy expenditure expressed in Kcal/Kg/15 min. If the subjects could not find an activity among those listed, they were asked to record the specific activity or activities in which they were engaged at the time. The instrument was translated from English into Portuguese, and then checked for accuracy and clarity of culturally sensitive or relevant terms. Test-retest was estimated in th a sample of 20 children, in the 6 grade, that are reported in Table 1. The records were converted to estimated energy expenditure using the categorical energy expenditure equivalents (Kcal/Kg/15min) suggested by Bouchard et al. (1983). Activities in categories 6 to 9 (median energy cost, ≥ 4.8 METS) were classified as moderate-to-vigorous in intensity (7, 8), which are recommended to develop and maintain health-related physical fitness in children and adolescents. Table 1. Descriptive statistic in the test-retest protocol of physical activity assessment provided by the diary. Statistics of the comparison of means between two time-moments and correlation. 1rt moment (n=23) 1848±592

EE week days, Kcal/day EE weekend day, 1924±475 Kcal/day EE total, 1873±504 Kcal/day EE (energy expenditure); * (p